Electrophotographic printers with detachably mountable developer cartridges are well known in the art. These printers are sometimes provided with a new-product sensing means for detecting information on a mounted developer cartridge, such as whether the developer cartridge is new.
In one proposed laser printer, a sensor gear is rotatably provided on the developer cartridge. A contact protrusion is provided on the sensor gear for contacting an actuator in a main casing of the laser printer. When the developer cartridge is mounted in the main casing, the sensor gear is driven to rotate so that the contact protrusion causes the actuator to pivot. A photosensor detects this pivoting of the actuator, enabling the laser printer to acquire information on the developer cartridge based on the detection results.